Respiration monitor

ABSTRACT

A system for respiration monitoring includes a garment, which is configured to be fitted snugly around a body of a human subject, and which includes, on at least a portion of the garment that fits around a thorax of the subject, a pattern of light and dark pigments having a high contrast at a near infrared wavelength. A camera head is configured to be mounted in proximity to a bed in which the subject is to be placed, and includes an image sensor and an infrared illumination source, which is configured to illuminate the bed with radiation at the near infrared wavelength, and is configured to transmit a video stream of images of the subject in the bed captured by the image sensor to a processor, which analyzes movement of the pattern in the images in order to detect a respiratory motion of the thorax.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/197,479, filed Nov. 21, 2018, which claims the benefit of U.S.Provisional Patent Application 62/589,587, filed Nov. 22, 2017, which isincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to sleep monitoring, andparticularly to apparatus, systems and methods for video-basedmonitoring of a sleeping infant.

BACKGROUND

Video-based sleep monitors for infants are known in the art. Forexample, U.S. Pat. No. 8,922,653 describes a crib mobile andsurveillance system which communicates video data captured by a camerawithin a mobile member housing, and sounds received by a microphonedisposed in a base, to a handheld monitor. The video data are displayedand broadcast in real time on a monitor screen on the handheld monitorto remotely monitor a child lain in a crib having the present device.

U.S. Pat. No. 9,530,080, whose disclosure is incorporated herein byreference, describes systems and methods for monitoring babies withcameras using a centralized computation and storage center that allowsusing visual output signals for computer vision and machine learninganalysis and high-level reasoning of baby movements. The systemcomprises a camera located at a predefined working point above a baby'scrib, and one or more communication networks between components of thesystem including a web-based network for in-depth computer vision andmachine learning analysis of the visual output signals by an analysisserver.

PCT International Publication WO 2017/196695, whose disclosure isincorporated herein by reference, describes a video monitoring system,which includes a camera head, including an infrared illumination sourceand an image sensor. A mount is configured to hold the camera head in afixed location and orientation above a crib, so that the image sensorcaptures images of the crib and an intervention region adjacent to thecrib from a fixed perspective.

As another example, U.S. Patent Application Publication 2013/0342693describes a video-enabled baby monitoring system including a transmitterwith a camera feature, which captures motion and includesmicroprocessors that generate a series of video signal codes, which aretransmitted at specific radio frequencies to a dedicated receiver unit.The transmitter unit also includes an infrared light source and a soundcapture source, wherein the sound capture source generates sound signalcodes. Another unit provides for enhanced, convenient data transfer fromthe transmitter unit and may be selected from a number of adaptordocking stations; or a smart phone platform; or a docking cradle withWi-Fi capability.

Systems for monitoring the breathing of a sleeping person are also knownin the art. For example, U.S. Patent Application Publication2004/0005083 describes a method and system for monitoring breathingmovement of an infant and for detecting and predictably estimatingregular cycles of breathing movements. Another disclosed aspect of theinvention is directed to detect and report irregularity of breathingactivity of an infant, such as cessation and non-periodicity, whichsuggests a likelihood of SIDS.

U.S. Patent Application Publication 2015/0105670 relates measurement ofvital signs such as a respiratory rate or a heart rate. In particular, asystem for determining a vital sign of a subject comprises an imagingunit for obtaining video data of the subject, a marker directly orindirectly attached to a body of the subject, wherein the markercomprises a graphical pattern, an image processing unit for detectingsaid marker in said video data, and an analysis unit adapted to extracta vital sign parameter related to the vital sign of the subject fromsaid video data and to determine the vital sign from said vital signparameter.

U.S. Patent Application Publication 2016/0345832 describes a system andmethod for monitoring biological status through contactless sensing thatincludes a sensing device with at least one video imaging device; asensor data processing unit, wherein the sensor processing unit when ina respiratory sensing mode is configured to extract a set of primarycomponents of motion from image data from the video imaging device; abiological signal processor that when in a respiratory sensing mode isconfigured to identify at least one dominant component of motion andgenerate a respiratory signal; and a monitor system.

SUMMARY

Embodiments of the present invention that are described hereinbelowprovide systems and methods for monitoring respiration of a sleepinginfant or other human subject.

There is therefore provided, in accordance with an embodiment of theinvention, a system for respiration monitoring, including a garment,which is configured to be fitted snugly around a body of a humansubject, and which includes, on at least a portion of the garment thatfits around a thorax of the subject, a pattern of light and darkpigments having a high contrast at a near infrared wavelength. A camerahead is configured to be mounted in proximity to a bed in which thesubject is to be placed, and includes an image sensor and an infraredillumination source, which is configured to illuminate the bed withradiation at the near infrared wavelength, and is configured to transmita video stream of images of the subject in the bed captured by the imagesensor to a processor, which analyzes movement of the pattern in theimages in order to detect a respiratory motion of the thorax.

In some embodiments, the human subject is an infant, the bed is a crib,and the garment includes a swaddling cloth. In one embodiment, theswaddling cloth is configured as a sack, having a size and shapesuitable for containing the body of the infant. Alternatively, theswaddling cloth is configured as a band, having a size and shapesuitable to surround the thorax of the infant.

In a disclosed embodiment, the pattern extends around both a front and aback of the thorax when the garment is fitted around the body of thesubject.

In some embodiments, the pattern includes an arrangement of light ordark geometrical shapes, which repeat across at least the portion of thegarment, and the processor is configured to identify and track thegeometrical shapes in the images in order to analyze the movement. In adisclosed embodiment, the shapes have respective corners, and theprocessor is configured to identify and track the corners in the imagesin order to analyze the movement.

Additionally or alternatively, the processor is configured to calibratea scale of the images responsively to a distance between the repeatingshapes. In one embodiment, the processor is configured to apply thescale in measuring the respiratory motion. Additionally oralternatively, the processor is configured to apply the scale inmeasuring one or more dimensions of the subject.

In a disclosed embodiment, the processor is configured to identify,responsively to the movement of the pattern, a deviation of at least oneof an amplitude and a rate of the respiratory motion from a predefinednormal range, and to issue an alert in response to the deviation.

There is also provided, in accordance with an embodiment of theinvention, a method for respiration monitoring, which includes providinga garment, which is configured to be fitted snugly around a body of ahuman subject, and which includes, on at least a portion of the garmentthat fits around a thorax of the subject, a pattern of light and darkpigments having a high contrast at a near infrared wavelength. A bed inwhich the subject is placed is illuminated with radiation at the nearinfrared wavelength. A video stream of images of the subject in the bedis captured while illuminating the bed at the near infrared wavelength.Movement of the pattern in the images is analyzed in order to detect arespiratory motion of the thorax.

The present invention will be more fully understood from the followingdetailed description of the embodiments thereof, taken together with thedrawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram that schematically illustrates a system forinfant sleep monitoring, in accordance with an embodiment of theinvention;

FIG. 2 is a schematic top view of a sleep monitoring device mounted overan infant's crib, in accordance with an embodiment of the invention;

FIGS. 3A and 3B are schematic front and back views, respectively, of aswaddling sack used in monitoring respiration of an infant, inaccordance with an embodiment of the invention;

FIGS. 4A and 4B are schematic outer and inner views, respectively of aswaddling band used in monitoring respiration of an infant, inaccordance with another embodiment of the invention; and

FIG. 5 is a flow chart that schematically illustrates a method forrespiration monitoring, in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF EMBODIMENTS Overview

Concern over proper respiration leads many parents of young infants tomonitor their child's nighttime breathing. A wide range of productofferings exist for this purpose, but they tend to be uncomfortable,unreliable, or both.

Embodiments of the present invention that are described herein offer anew solution to the problem of infant respiration monitoring, using anovel garment, which facilitates both reliable detection of respiratorymotion and infant comfort, while fitting snugly around the infant'sbody. (“Snug” in this context means that the garment fits tightly enoughso that the cloth will expand and contract as the infant's thoraxexpands and contracts in respiration, without being so tight as toconstrict respiratory motion.)

Substantially any suitable type of garment can be used for the presentpurposes. By way of example, the embodiments described below referspecifically to a swaddling cloth, such as a swaddling sack, having asize and shape suitable for containing the entire body of the infant, ora swaddling band, which fits around the thorax. The use of a swaddlingcloth is advantageous in promoting both sound sleep and reliablemonitoring. The principles of the present invention, however, are by nomeans limited to this type of garment, and may alternatively be appliedin monitoring the respiration of other subjects, including olderchildren, as well as adults.

Regardless of the specific configuration, the garment comprises apattern of light and dark pigments on at least a portion of the garmentthat fits around the thorax of the subject. The light and dark pigmentsare chosen so that the pattern has a high contrast at a near infrared(NIR) wavelength, meaning specifically a wavelength between 800 nm and1500 nm. This wavelength range is useful due to the availability ofintense, inexpensive solid-state light sources, such as light-emittingdiodes (LEDs), and the sensitivity of common image sensors in thisrange, while being invisible to human eyes. The terms “light” and “dark”in relation to the pigments mean, in the context of the presentdescription and in the claims, that the “light” pigment reflects atleast 50% of the incident radiation at a chosen illumination wavelengthin the NIR, while the “dark” pigment reflects less than 20% of theincident light at this wavelength. The term “high contrast” in thiscontext means that when the pattern is illuminated uniformly at thechosen wavelength, the intensity of reflected light received by theimage sensor from the light pigment is at least twice that received fromthe dark pigment.

In the disclosed embodiments, a camera head is mounted in proximity to abed in which the subject is to be placed. The camera comprises an imagesensor and an infrared illumination source, which illuminates the cribat a chosen wavelength in the NIR. The image sensor captures images ofthe subject in the bed (for example, of an infant in a crib, as shown inthe figures that are described below). The camera head transmits a videostream of these images to a processor, which analyzes movement of thepattern in the images in order to detect the respiratory motion of thethorax. When the processor detects a deviation of the amplitude and/orrate of the respiratory motion from a predefined normal range, it issuesan alert and thus enables a caregiver to intervene immediately. Thegarment can be designed so that the pattern extends around both thefront and the back of the thorax; the respiratory motion can thusmonitored reliably regardless of whether the subject is lying on his orher front, back or side. Alternatively, the pattern may appear only thefront of the thorax.

In some embodiments, the pattern comprises an arrangement of light ordark geometrical shapes, which repeat periodically across at least theportion of the garment that extends across the thorax. This sort ofpattern facilitates fast and accurate processing of the images by theprocessor. For example, the processor can identify corners of thegeometrical shapes and track these corners in the images in order toanalyze the movement of the pattern.

When the actual, physical sizes of the shapes on the swaddling cloth areknown, the processor can calibrate the scale of the images based on thedistance (in pixels) between the repeating shapes in the images, and canthen apply this scale in measuring the respiratory motion and/ormeasuring one or more dimensions of the subject. These lattermeasurements include, but are not limited to, the distance an infantbeing monitored traveled in a crib, the distance crawled, the magnitudeof head movements, the magnitude of limb movements, the magnitude oftwitches, head circumference, head shape, head volume, height, bodyvolume, weight and BMI estimations, limb length, distance between theeyes, forehead height, general facial dimensions, shoulder width, hipwidth, hip angles, foot angles, torso length. The calibrated scale canalso be used to improve object detection algorithms by normalizing theimage size to minimize the size tolerance of detection of objects suchas the crib, the infant, and its head.

Although the figures and the embodiments described below refer tocertain specific swaddling cloth designs, with a certain pattern shownby way of example, other sorts of garments and other patterns that canbe used for the present purposes will be apparent to those skilled inthe art after reading the present description. All such alternativeembodiments are considered to be within the scope of the presentinvention.

System Description

FIG. 1 is a block diagram that schematically illustrates a system 20 forinfant sleep monitoring, in accordance with an embodiment of theinvention. System 20 comprises a monitoring camera head 22, which ismounted in a fixed location and orientation above a crib 24, in which aninfant 26 is sleeping in a residence 28. Alternatively, camera head 22may be mounted in another suitable location in proximity to the crib,mounted on a wall or tabletop, for example.

For purposes of image capture, an infrared (IR) light-emitting diode(LED) 25 on the lower side of camera head 22 illuminates the sleepinginfant 26. A diffuser can be used to spread the infrared light uniformlyacross the crib. Camera head 22 also comprises an infrared-sensitiveimage sensor 23, which may conveniently have a standard 4:3 aspect ratioto fit the size of a standard crib 24. The resolution and sensitivity ofimage sensor 23 can be optimized for night conditions, and specificallyfor the wavelength range of LED 25. Further details of camera head 22,including its internal components and modes of operation, are describedin the above-mentioned PCT International Publication WO 2017/196695(particularly in FIGS. 4A/B and 5 and the corresponding description inthe specification on pages 8-9). This PCT publication also describesdifferent ways of mounting the camera head above or alongside the crib.

Camera head 22 transmits digitized streaming video, and possibly othersignals, as well, over a local network to a router 30, typically via awireless local area network (LAN) link, such as a Wi-Fi connection, or awired link, such as an Ethernet connection. Camera head 22 transmits thedigitized video data in packets that are addressed so that router 30forwards the video packets both to a local client device 32 on the localnetwork and via a public network 36, such as the Internet, to a remoteserver 38. Client device 32 typically comprises a smart phone, tablet orpersonal computer, which enables a caregiver 34 in another room ofresidence 28 to monitor infant 26, even when there is no Internetconnection available. Server 38 makes video images and other dataavailable to authorized remote client devices 44, thus enabling acaregiver 46 to monitor infant 26 at any location where there is accessto public network 36. The Wi-Fi or other local network connectionprovides reliable video streaming from camera head 22 to client device32 with high bandwidth and low latency, even if the external Internetconnection is not working. As long as the Internet is connected,however, the video stream is also transmitted to server 38 for purposesof analysis and retransmission.

Server 38 typically comprises a general-purpose computer, comprising aprocessor 40 and a memory 42, which receives, stores and analyzes imagesfrom camera head 22 in residence 28 and similarly from other cameras inother residences (not shown). In the present embodiment, processor 40analyzes the images in order to detect and measure respiratory motion ofthe thorax of infant 26, and to provides caregivers 34 and 46 withreports and (when required) alerts regarding the infant's breathingpatterns. Processor 40 typically performs these functions under thecontrol of software, which may be downloaded to server 38 in electronicform, over a network, for example, as well as stored on tangible,non-transitory computer-readable media, such as magnetic, optical orelectronic memory media. Alternatively or additionally, some or all ofthese processing and monitoring functions may be performed locally, forexample by a microprocessor in camera head 22 and/or by suitableapplication software running on processors in client devices 32 and/or44.

FIG. 2 is a schematic top view showing details of the deployment and useof monitoring camera head 22 over crib 24, in accordance with anembodiment of the invention. Infant 26 in crib 24 is wrapped in aswaddling sack 52, with a periodic pattern printed on a portion 54 ofthe swaddling sack that fits around the infant's thorax. In thisembodiment, monitoring camera head 22 stands against a wall over crib24. Camera head 22 is held, for example, at the end of an arm at theupper end of a tripod mount behind crib 24, at the midpoint of the longside of the crib. Camera head 22 in this embodiment is positioned andadjusted so that the camera head has a field of view 50 from a fixedperspective that encompasses at least the area of crib 24. Thisperspective provides server 38 with image information that can beanalyzed conveniently and reliably to detect respiratory motion ofinfant 26. Alternatively, the camera head may be mounted in any othersuitable location in proximity to crib 24 that gives a view of theinfant that is suitable for monitoring movement of the pattern on theswaddling cloth or other garment.

FIGS. 3A and 3B are schematic front and back views, respectively, ofswaddling sack 52, which is used in monitoring the respiration of infant26, in accordance with an embodiment of the invention. Before puttinginfant 26 into crib 24, the caregiver inserts the infant into swaddlingsack 52, and then fastens a band 58 snugly around the infant's thorax.Hook and loop patches 60 and 62 (such as Velcro® patches) may be usedfor this purposes, or any other suitable type of fastener that is knownin the art.

Portion 54 of swaddling sack 52 comprises a periodic pattern of lightand dark pigments, extending around both the front and back of sack 52,with a high contrast at the near infrared wavelength of LED 25. In thisexample, the pattern comprises two types of dark geometrical shapes 56,but alternatively other patterns may be used, with one or more differentshapes, in either dark or light pigment. The sharp corners of the shapesin this example facilitate detection and tracking of the shapes by animage processor for the purpose of detecting respiratory motion. Thedimensions of shapes 56 are typically between 5 and 50 mm, and camerahead is designed so that each shape will have an extent between 3 and 30pixels in the images captured by image sensor 23, although larger orsmaller shapes and magnifications may alternatively be used.

FIGS. 4A and 4B are schematic outer and inner views, respectively, of aswaddling band 70 used in monitoring respiration of an infant, inaccordance with another embodiment of the invention. The size and shapeof band 70 are suitable to surround the thorax of an infant, with theband fastened snugly around the thorax by hook and loop patches 72 and74. Band 70 leaves the infant free to move his or her arms and legs, incontrast to sack 52. The pattern of shapes 56 on band 70 is similar tothat on sack 52, as described above.

Monitoring of Respiratory Motion

FIG. 5 is a flow chart that schematically illustrates a method forrespiration monitoring, in accordance with an embodiment of theinvention. This method is described hereinbelow, for the sake ofconcreteness and clarity, with reference to the elements of system 20and swaddling sack 52, as shown and described above. Alternatively, themethod may be applied, mutatis mutandis, in other system configurationsand/or using other sorts of swaddling cloth, as noted earlier.Specifically although certain image processing functions andcommunication functions are described below as being carried out byserver 38, at least some of these functions may be carried out by othermeans, such as client devices 32 and 44 and/or a processor (not shown)that is embedded in camera head 22.

Processor 40 initiates the method of FIG. 5 upon receiving a videostream from camera head 22 and a signal (for example from the camerahead or from client device 32) indicating that monitoring is to begin.Processor 40 finds a region of interest (ROI) that contains a part ofthe pattern on swaddling sack 52 in an initial image frame, at an ROIidentification step 80. The ROI may be identified automatically byanalyzing the image to locate the pattern on swaddling sack 52 (orswaddling band 70, for example). Processor 40 may access features of thepattern or patterns that are used on various types of swaddling cloth,such as the sizes and forms of shapes 56, in memory 42, in order toidentify the ROI more easily. Alternatively or additionally, thecaregiver may indicate the location of the ROI to the processor, forexample by pointing to the ROI in an image from camera head 22 that isdisplayed on client device 32.

In some embodiments, processor 40 finds the locations of the corners ofshapes 56 in the ROI on swaddling sack 52, at a corner finding step 82.(“Corners” are not necessarily right angles, and can be formed that themeeting point of edges at different angles, for example angles rangingbetween 60° and 120°.) Corners can be found by filtering the part of theimage that is contained in the ROI with filters that are matched to thegeometrical features of the pattern, for example. Once the corners arefound, processor 40 can calibrate the scale of the images by comparingthe distance between the repeating shapes in the images to the knowndistance between the geometrical features on the swaddling sack.

Once the ROI and pattern features have been identified in the initialimage, processor 40 receives and processes succeeding images in thevideo stream, at an image input step 84. In each image, the processortracks the movement of each of the corners in the ROI that wasidentified previously. This step may use techniques such as featuremapping or the Kanade-Lucas-Tomasi (KLT) feature tracking algorithm inorder to measure motion from frame to frame with sub-pixel accuracy. Ifthe ROI is lost in a given image or sequence of images, for example dueto large movements of infant 26, processor 40 may search over an entireimage in order to recover the location of the ROI and may then return tostep 80.

Alternatively or additionally, processor 40 may apply other sorts ofimage processing algorithms in identifying and tracking movement of thepattern, not necessarily depending on corners. For example, templateshift registration can be used to track shapes having no clear corners(such as circles). As another example, normal flow algorithms can beused in tracking object edges.

Since respiratory movement from one frame to the next is very small,processor 40 averages the motion of each corner (or other feature) overmultiple successive frames and/or multiple feature locations, at amovement averaging step 88. When infant 26 is breathing, the infant'sthorax expands and contracts periodically, so that all of the cornerswithin a given ROI on swaddling sack 52 will move in the same directionfrom frame to frame, with a temporal variation that is approximatelysinusoidal. The average movement will therefore be substantial. (The ROIis chosen at step 80 to be large enough to contain multiple shapes 56,but small enough so that all the shapes in the ROI move in the samedirection during respiration.) On the other hand, when infant 26 is notbreathing, the directions of movement of the different corners will berandom and will thus cancel out upon averaging. Processor 40 may alsoidentify large movements that are not periodic as corresponding to theinfant moving in his or her sleep or being awake.

Processor 40 analyzes the averaged movement signal over time in order todetect periodic motion that is characteristic of respiration, at amovement analysis step 90. For this purpose, processor 40 may filter theaveraged signal using a set of bandpass filters with frequency bandsdistributed through the range of normal respiration frequencies. Forexample, processor 40 may apply a set of six bandpass filters thattogether span the normal breathing range, which is about 20-60breaths/minute for infants under one year old. Any suitable type ofbandpass filter with sufficiently sharp edges may be used for thispurpose, for instance a fifth-order Butterworth filter, as is known inthe art. Alternatively, larger or smaller numbers of filters, of this orother types, may be used, depending upon the available computing powerand the level of precision that is required to avoid false alarms.

After filtering the signal at step 90, processor 40 chooses thefrequency band with the highest amplitude, at a band selection step 92.Processor 40 compares this amplitude to a preset threshold, at a motionchecking step 94. If the amplitude is below threshold, and remains belowthreshold for longer than a preset time limit, processor 40 issues analert, at an alarm step 96. Infants may normally stop breathing forshort periods, typically up to 20 sec, and then resume breathingnormally. The time limit at step 94 may thus be set, for example, to 20sec. If processor 40 does not detect respiratory motion of sufficientamplitude over a period longer than this limit, it may send anotification to client device 32 at step 96, for instance, or take moredrastic action, such as triggering a visible and/or audible alarm inresidence 28. For example, processor 40 may activate a visible lightand/or audio speaker in camera head 22.

When processor 40 detects respiratory motion of sufficient amplitude atstep 94, it also checks the infant's respiratory frequency, at a ratechecking step 98. If the highest motion amplitude was found to be in thehighest or lowest frequency band of the filters applied at step 92, forexample, the processor may conclude that the breathing rate isabnormally high or low. In this case, too, processor 40 will issue analert at step 96. Otherwise, the processor concludes that the infant'sbreathing is normal and continues to capture and analyze further imagesas described above. Optionally, processor 40 may continually issueupdates to client devices 32 and 44, even when infant 26 is breathingnormally, to indicate the breathing status and respiratory rate of theinfant.

As noted earlier, although the embodiments described above relatespecifically to infant respiration monitoring, using a patternedswaddling cloth, the principles of the present invention may similarlybe applied using other sorts of garments with suitable pattern, not onlyfor infants but also for older subjects. It will thus be appreciatedthat the embodiments described above are cited by way of example, andthat the present invention is not limited to what has been particularlyshown and described hereinabove. Rather, the scope of the presentinvention includes both combinations and subcombinations of the variousfeatures described hereinabove, as well as variations and modificationsthereof which would occur to persons skilled in the art upon reading theforegoing description and which are not disclosed in the prior art.

The invention claimed is:
 1. A system for respiration monitoring,comprising: a garment, having a size and shape suitable to surround andfit snugly around a body of a sleeping infant, and which comprises, onat least a portion of the garment that fits around a thorax of theinfant, a pattern of light and dark pigments having a high contrast at anear infrared wavelength and extending around a front, a back and sidesof the thorax when the garment is fitted around the body of the infant,wherein the pattern comprises an arrangement of light or darkgeometrical shapes, which repeat across at least the portion of thegarment; and a camera head, which is configured to be mounted inproximity to a bed in which the infant is to be placed, and whichcomprises an image sensor and an infrared illumination source, which isconfigured to illuminate the bed with radiation at the near infraredwavelength, and which is configured to transmit a video stream of imagesof the infant in the bed captured by the image sensor to a processor,which analyzes movement of the pattern in the images in order to detecta respiratory motion of the thorax, wherein the processor is configuredto calibrate a scale of the images responsively to a distance betweenthe repeating shapes, and wherein the shapes have respective corners,and the processor is configured to identify and track the corners in theimages in order to analyze the movement.
 2. The system according toclaim 1, wherein the processor is able to detect the respiratory motionof the thorax regardless of whether the infant is lying on his or herfront, back or side.
 3. The system according to claim 1, wherein thegarment is configured as a sack, having a size and shape suitable forcontaining the body of the infant.
 4. The system according to claim 1,wherein the processor is configured to apply the scale in measuring therespiratory motion.
 5. The system according to claim 1, wherein theprocessor is configured to apply the scale in measuring one or moredimensions of the infant.
 6. The system according to claim 1, whereinthe processor is configured to identify, responsively to the movement ofthe pattern, a deviation of at least one of an amplitude and a rate ofthe respiratory motion from a predefined normal range, and to issue analert in response to the deviation.
 7. A method for respirationmonitoring, comprising: providing a garment, having a size and shapesuitable to surround and fit snugly around a body of a sleeping infant,and which comprises, on at least a portion of the garment that fitsaround a thorax of the infant, a pattern of light and dark pigmentshaving a high contrast at a near infrared wavelength and extendingaround a front, a back and sides of the thorax when the garment isfitted around the body of the infant, wherein the pattern comprises anarrangement of light or dark geometrical shapes, which repeat across atleast the portion of the garment; illuminating a bed in which the infantis placed with radiation at the near infrared wavelength; capturing avideo stream of images of the infant in the bed while illuminating thebed at the near infrared wavelength; and analyzing movement of thepattern in the images in order to detect a respiratory motion of thethorax, wherein analyzing the movement comprises calibrating a scale ofthe images responsively to a distance between the repeating shapes, andwherein the shapes have respective corners, and analyzing the movementcomprises identifying and tracking the corners in the images.
 8. Themethod according to claim 7, wherein analyzing the movement comprisesdetecting the respiratory motion of the thorax regardless of whether theinfant is lying on his or her front, back or side.
 9. The methodaccording to claim 7, wherein the garment is configured as a sack,having a size and shape suitable for containing the body of the infant.10. The method according to claim 7, wherein analyzing the movementcomprises applying the scale in measuring the respiratory motion. 11.The method according to claim 7, and comprising applying the scale inmeasuring one or more dimensions of the infant.
 12. The method accordingto claim 7, wherein analyzing the movement comprises identifying,responsively to the movement of the pattern, a deviation of at least oneof an amplitude and a rate of the respiratory motion from a predefinednormal range, and issuing an alert in response to the deviation.